Model Based Characterization of Transient Response of a Solid Oxide Fuel Cell System

Abstract

In this paper we perform transient analysis of a Solid Oxide Fuel Cell (SOFC) system. We consider a steam reformer based SOFC system with anode recirculation and with methane as fuel. For the analysis, we develop a control-oriented model that captures the details of heat and mass transfer, chemical kinetics and electrochemistry of the SOFC system. The coupled dynamics of the steam reformer and the fuel cell anode control volumes are extracted and through coordinate transformations we derive closed-form expressions characterizing the steady-state and transient behaviors of two critical performance variables of reformer-based SOFC systems, namely utilization and steam-to-carbon balance. Our analysis is supported by simulations. Using the results derived, we address steady-state fuel optimization by posing it as a problem in linear programming. Our results can be applied in predicting system response to step changes in current and will be useful in designing control strategies for SOFC based power plants.

Robust nonlinear control of fuel cell ultra-capacitor hybrid system

“…where, X 1,a , X 2,a , X 4,a , and X 1,r , X 2,r , X 4,r , represent the molar concentrations of CH 4 , CO and H 2 in the anode and the reformer respectively, [12], [3]. U is sensitive to fuel cell current i f c .…”

Closed-Form Formulation of the Thermodynamically Consistent Electrochemical Model Considering Electrochemical Co-Oxidation of CO and H2 for Simulating Solid Oxide Fuel Cells

“…However, the present system level models of SOFCs, for example [16][17][18][19][20][21][22][23][24][25][26] that are applied in performance [16][17][18]20,21,[23][24][25] and service life [19,22] predictions, and optimisations do not feature both of these requirements, i.e., the derivation of activation losses and utilisation ratios for multiple fuel species in a closed-form, and physicochemical consistency. Models, such as [16][17][18][19][20][21][22][23]26], model from the electrochemical point of view of only a single reactant component fuel (hydrogen) and neglect the CO, and calculate its effects only via energy balances or via the water-gas shift reaction (WGSR) without addressing the kinetics of electrochemical co-oxidation.…”

“…Models, such as [16][17][18][19][20][21][22][23]26], model from the electrochemical point of view of only a single reactant component fuel (hydrogen) and neglect the CO, and calculate its effects only via energy balances or via the water-gas shift reaction (WGSR) without addressing the kinetics of electrochemical co-oxidation. On the other end, these models aiming to address multi-component kinetics observed in SOFC are also being developed [24,25,[27][28][29][30][31][32][33][34][35][36][37]; however, they are usually embedded in higher fidelity models [27][28][29][30][31][32][33][34][35][36][37], ranging from 1D+1D [25] over 2D [28,29,31,32,[34][35][36][37] to 3D [29,30]. For a more in-depth review of these and other models, the reader is referred to the review article published by Bao et al [38].…”

“…For a more in-depth review of these and other models, the reader is referred to the review article published by Bao et al [38]. In References [24,25,[39][40][41][42][43], the authors model multi-reactant fuel electrochemistry on the system level and are thus physicochemically consistent. However, the electrochemical models utilised in [24,25,[39][40][41]43] obtain the overall voltage and over-potentials with a linearised Tafel equation or in an iterative manner, which inherently leads to increased computational times, preventing their use in SoX and HiL applications.…”

“…In References [24,25,[39][40][41][42][43], the authors model multi-reactant fuel electrochemistry on the system level and are thus physicochemically consistent. However, the electrochemical models utilised in [24,25,[39][40][41]43] obtain the overall voltage and over-potentials with a linearised Tafel equation or in an iterative manner, which inherently leads to increased computational times, preventing their use in SoX and HiL applications. In contrast, in [42,44], the approximate solution is obtained by decoupling the charge and mass transfer and by neglecting the effect of species concentration on electrochemical kinetics.…”